Winter Storm

Snow Possible in Seattle and Portland Areas as Western Storm Parade Returns

At a Glance

Rain and heavy mountain snow will continue to impact parts of the West into early this week.
Snow is also possible in lower elevation areas, including Seattle and Portland late Sunday-Monday.
Multiple feet of snow will pile up in California's Sierra through Tuesday.
Heavy rain will also return to lower elevations of California.

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The West Coast is dealing with yet another round of stormy weather to begin this week, including the possibility of snow for lower elevations of the Pacific Northwest, while feet of snow pile up in California's Sierra Nevada.

On the warmer side of this weather pattern, lower elevations of northern California may see several more inches of rain early this week, raising the risk of more debris flows and possible flooding.

(MORE: Portland May Be America's Most Winter-Fatigued City)

The National Weather Service has issued winter storm warnings for California's Sierra Nevada, as well as parts of the northern Rockies and interior lower elevations of Washington. Winter weather advisories are now in effect for western Washington and northwest Oregon, including the Seattle and Portland areas.

(MORE: 'Januburied': Snow Breaks Records in the Sierra Nevada)

Below are the daily details to start this week, followed by potential snow and rain amounts.

Through Sunday Night

Another Pacific frontal system slides into northern California, Oregon and Washington later Sunday with abundant rain and snow.
Snow levels may lower to near sea level in western Washington and northwest Oregon, leading to the chance of accumulations in the Seattle metro area and possibly the Portland area, beginning Sunday or Sunday night.
Seattle is the most likely location to receive snowfall accumulations, but Portland could also see snow or rain mixed with snow depending on how much the air mass cools off. Areas above 700 feet in elevation are most likely to receive significant snow in the Portland area, though some accumulations are possible on the valley floor.
Interior areas of the Northwest will also see snow, including Spokane.
Heavy snow will impact California's Sierra Nevada Sunday night.
Strong wind gusts are also possible at times, especially in southern Oregon and California.

Monday

Rain and mountain snow will persist across the West coast and into much of the Pacific Northwest and Rockies.
Accumulating snow will continue to be possible in the Seattle area and possibly the Portland metro area into Monday. Again, areas above 700 feet in elevation have the best chance at significant snowfall in the Portland area. Some accumulations remain possible at the valley floor.
Heavy snow will continue to impact the Sierra Nevada. Snow will also affect parts of the northern and central Rockies.
Gusty winds are also expected, including northern California, southern Oregon and western Nevada.

Tuesday

Another surge of moisture associated with an area of low pressure will arrive Monday night through Tuesday.
California will take the brunt of this system, though snow will also impact other areas of the mountain West with rain in valleys.
This will likely be a warmer system with rising snow levels in the Sierra Nevada above 8,000 feet.
Some flooding and debris flows are possible from this storm in northern and central California.

If that wasn't enough, another Pacific frontal system will push into the West late this week, bringing more rain and mountain snow to northern California, the Pacific Northwest, and parts of the Rockies.

(MAPS: 7-Day U.S. Rain/Snow Forecast)

How Much Snow and Rain

Snow

Some slushy accumulation of snow is possible in the lowlands of western Washington and possibly western Oregon, including Seattle and Portland, Sunday into Monday.
Seattle is the most likely city to see snowfall accumulations. Slightly higher terrain areas around the Portland area also have a greater chance of seeing accumulations.
Snow levels will be as low as 6,000 feet in the Sierra with 1 to 2 feet of snow possible. Higher terrain areas will see 2 to 4 feet of snow. Expect hazardous mountain travel near Sierra pass levels through Tuesday morning.
The mountains of northwest Wyoming, Idaho, northeast Oregon, northwest Montana and the Cascades could also see at least a foot of snow.
FORECAST: Seattle | Portland

Rain

A broad swath of 1 to 3 inches of rainfall is expected across the West Coast through Tuesday.
Higher-elevation locations below snow level in northern California and coastal Oregon could see 3 to 8 inches of rain through Tuesday.
Lighter amounts, generally less than 1 inch, are expected in Southern California.
Flooding may become a concern in any areas of northern California that receive heavier rainfall over the next few days.
Debris flows are also possible.
FORECAST: San Francisco | Los Angeles

Storm Reports

On Friday, yet another freezing rain event occurred in parts of the Pacific Northwest's Interstate 5 corridor, including Portland, Oregon.

Icy roads lead to numerous accidents in the Portland metro area early Friday morning. Several reports of flooding and even hail occurred on Friday afternoon near Fresno, California.

Selected snow, ice and rain reports as of 7:30 p.m. PST Saturday:

Snow: